The mission ofthe Comparative Pathology Shared Resource (CPSR) is to provide full-service pathology support for Masonic Cancer Center (MCC) members who use animal subjects in their laboratory and clinical research. CPSR is a critical resource for projects utilizing animal tissues and is essential for publications involving pathological changes in tissues. M. Gerard O'Sullivan, MVB, PhD, took over the leadership of CSPR in 2009; Dr. O'Sullivan has more than 20 years of experience in comparative and experimental veterinary pathology. Also in 2009, CPSR recruited a very experienced histotechnologist, Paula Overn. Three histotechnicians prepare appropriately processed fixed or frozen tissues for histology and immunohistochemistry. Particular strengths ofthe Shared Resource are in doing non-routine challenging or tedious histological preparations that require special handling, such as sectioning and performing immunohistochemistry on bone. Board-certified veterinary pathologists provide expert gross and histopathologic analyses, generate high-resolution digital images of specimens, and provide intellectual input on study design and manuscript preparation for research projects and grant applications. The CPSR also has considerable experience in developing new protocols and techniques and has developed approximately 60 new immunohistochemistry markers since 2008. In addition, the CPSR has developed double-labeling techniques to simultaneously detect several combinations of proteins. Requests for quantification of marker expression and histomorphometric evaluations have increased, and CSPR has gained access to equipment and software to accommodate these requests. Weekly staff meetings and the oversight of an advisory committee composed of CPSR users ensure that the resource is able to meet the needs of MCC members for veterinary pathology.